Sealing assembly

ABSTRACT

A sealing assembly including a slipper seal and an elastomeric seal with one of the seals circumscribing the other of the seals. The slipper seal includes first and second end portions separated by a central portion with the central portion having a circumferential surface adapted to slidingly and sealingly engage a member. The circumferential surface is generally flat in axial cross section and the first and second end portions taper radially away from such member so that they do not engage such member.

United States Patent Traub 51 May 16, 1972 54] SEALING ASSEMBLY3,268,235 8/1966 Jacobellis ..277/165 72] Inventor: Henry A. TrauhPacific Palisades, Cam 3,149,848 9/1964 Galloway .....277/ 165 [73]Assignee: W. S. Shamban & Co., Los Angeles, Calif. Pr maryExaminer-Robert 1. Smith Att0rney-Smyth, Roston & Pavitt [22] Filed:July 2, 1970 21 Appl. No.2 51,950 ABSTRACT A sealing assembly includinga slipper seal and an elastomeric 52 us. Cl ..277/165 Seal with We Sealscircumscribing the seals- 51] Int Cl The slipper seal includes first andsecond end portions l f h ;277 165 Separated by a central Portion withthe central portion having [58] d 0 seam a circumferential surfaceadapted to slidingly and sealingly en- [5 6] References Cited gage amember. The circumferential surface is generally flat in axial crosssection and the first and second end portions taper UNITED STATESPATENTS radially away from such member so that they do not engage suchmember. 3,418,001 12/1968 Rentschler ..277/165 3,033,578 5/1962 Kellogg..277/165 9 Claims, 10 Drawing Figures PATENTEDHAY 16 I972 3.6631124 sum1 OF 2 INVENTOR= HenrY A. Traub W m M I? ATTORNE YS PATENTEIJMAY 16 19723, 663 024 INVENTORI Hem? A. Traub j 3 A rroeilg Z SEALING ASSEMBLYBACKGROUND OF THE INVENTION Sealing assemblies are often utilized toprovide a substantially fluid tight seal between relatively movableinner and outer members. For example, the outer member may includeaxially spaced radial walls defining a generally annular groove forreceiving the sealing assembly. The sealing assembly is provided in suchgroove and sealingly engages both of the members.

For some applications resiliently deformable elastomeric seals such asO-rings generally provide a good seal. However, when the members betweenwhich the seal is to be formed are relatively movable, it is oftendesirable to employ a slipper seal to substantially reduce the wear onthe elastomeric seal. Slipper seals are constructed of relatively hard,wear resistant materials and as such are adapted to withstand rubbingcontact.

In one such construction, the slipper seal has a cylindrical innersurface for slidably engaging the inner member and an outercircumferential surface which is arcuate in axial cross section. Theelastomeric seal is radially compressed between the circumferential wallof the groove and the outer circum ferential surface of the slipper sealto thereby urge the cylindrical surface of the slipper seal intoengagement with the inner member. When fluid under relatively highpressure is supplied to the seal assembly, the pressure acts directlyagainst the elastomeric seal to load the latter and cause theelastomeric seal to apply greater radial inward force on the slipperseal. Because of the high force which is supplied to the slipper seal atrelatively high fluid pressure, this type of seal is quite effective asa high pressure seal. 7

However, one problem with this type of seal is that it is notparticularly effective at relatively low fluid pressures. One reason forthis is that the slipper seal is typically constructed of relativelyhard plastic material such as polytetrafluoroethylene which isdeformable only under relatively high pressure. The force applied to theslipper seal due to radial compression of the elastomeric seal is notnormally sufficient, absent the benefits derived from high fluidpressure, to cause the slipper seal to form an adequate low pressureseal with the inner member.

Another sealing assembly of the type employing a slipper seal and aresilient member to urge the slipper seal into sealing contact is shownin U.S. Pat. No. 3,223,426. This sealing assembly utilizes a generallychannel-shaped slipper seal engageable with both of the relativelymovable members and a spring which is received within the channel. Oneproblem with this construction is that the sealing assembly sealsagainst fluid pressure from one direction only. Secondly, the knifeedges on the slipper seal would undoubtedly be subject to relativelyrapid wear due to the extremely small area of contact between theseknife edges and the members they engage. This wear results in reducedcompression of the spring. The spring has a relatively steepforce-deflection curve, and therefore the low pressure effectiveness ofthe seal assembly is impaired. Third, deformation of the Teflon envelopeunder pressure is followed up by the spring. The force applied by thespring is further reduced and applied over a larger area. This canresult in deterioration of the low pressure performance of the sea] as aresult of reduced unit loading.

SUMMARY OF THE INVENTION The present invention provides a sealingassembly which has substantially improved low pressure sealingcharacteristics. According to one aspect of the invention this result isachieved, at least in part, by reducing the area of contact between theslipper seal and the member which it sealingly engages. By reducing thisarea of contact, the unit loading of the slipper seal against suchmember is increased. For example, if the area of contact is reduced by50 percent, the unit loading of the slipper seal against the memberwhich it sealingly engages will double.

The sealing assembly isadapted for use between relatively movable innerand outer members. For convenience in much of the description, thesealing assembly is described as an ID.

seal in which the sealing assembly is located in a groove in the outermember and the slipper seal sealingly engages the inner member. Itshould be understood, however, that the concepts of this invention arenot limted to an ID. seal and that they are equally applicable to an OD.seal.

The slipper seal includes a central region and first and second endportions extending axially of the central portion with all of suchportions circumscribing the inner member. The central region has aninner circumferential surface which slidably and sealingly engages theinner member.

Normally it is desired to maintain the end of the slipper seal facingthe fluid under pressure tightly in contact with the inner member. Thepresent invention departs from this conventional practice by separatingboth of the end portions of the slipper seal from the inner member tothereby achieve the unexpected result of a seal having improvedeffectiveness at both high and low pressures.

The percent of the axial length of the slipper seal which contacts theinner member can be varied depending upon the amount of unit loadincrease necessary or desirable for a particular application. The axialdimension of the circumferential surface of the central region shouldpreferably be more than nominal but substantially less than the fullaxial dimension of the slipper. Thus, the amount that the area ofcontact is reduced is more than that which would be achieved from aconventional chamfer.

The circumferential surface of the central region generally conforms toan axial length of the'member which it sealingly engages. For example,if the inner member is cylindrical, the circumferential surface is alsopreferably cylindrical and thus flat in axial cross section. If thecircumferential surface of the central region is flat in axial crosssection rather than pointed, it will wear much less rapidly.

The central region also cooperates in an advantageous manner with theelastomeric ring. The elastomeric ring should be held in radialcompression between the circumferential wall of the groove and thecentral region of the slipper seal with the force of such radialcompression acting radially inwardly on the central region of theslipper seal to load the circumferential surface tightly against theinner member. Stated differently, the central axis of the elastomericring and the midpoint of the central region should lie substantially inthe same radial plane so that the force of radial compression of theO-ring will act centrally through the central region rather than on theend portions of the slipper seal. in addition, the footprint of theelastomeric seal should not extend substantially over the end portionsof the slipper seal. The footprint of the elastomeric seal is the areaof contact between the elastomeric seal and the slipper seal when thesealing assembly is installed in the groove between the inner and outermembers and when no fluid under pressure is supplied to the sealingassembly. This assures that no substantial radial inward pressure willbe applied, under low fluid pressure conditons, by the O-ring to the endportions of the slipper seal. lf substantial force were applied from theelastomeric seal to the end portions, at least some of such force may beutilized in bending of the end portions radially inwardly relative tothe central portion.

The sealing assembly of this invention is adapted to be dynamicallyloaded by fluid under pressure. When this occurs, fluid under pressureenters the groove from one end of the groove and urges the elastomericring in the opposite direction. The fluid under pressure appliescompressive forces to the elastomeric ring which exerts a radial inwardforce on the slipper seal tending to force the latter into tightersealing contact with the innermember. The fluid under pressure forcesthe elastomeric ring over one of the end portions and as the pressureincreases, it ultimately becomes sufficient to deform such end portionradially inwardly into sealing contact with the inner member.Thereafter, both the central region and such end portion engage theinner member. Although this increases the area of contact between theinner member and the slipper seal, this does not occur until. the fluidpressure is sufficiently high so that there is no danger of exceedingthe allowable leakage tolerance.

According to another aspect of the invention, the low pressure sealingcharacteristics of the sealing assembly are improved by provinging meansfor relatively ghighly compressing the resilient deformable seal in theradial direction. This causes the deformable seal to urge the slipperseal against the cooperating member with greater force. This canadvantageously be accomplished by providing an annular ridge around thecentral region of the slipper seal thereby additionally radiallycompressing the adjacent portions of the deformable seal.

The ridge can be permanently formed on the slipper seal as by machining.Alternatively, the ridge can be provided in response to the positioningof the slipper seal in the groove between the members. In order toaccomplish this, the slipper seal should form a medium or heavyinterference fit with the member which it is to sealingly engage andsurround. In addition, the slipper seal should be deformable about acentral circumferentially extending axis and the cross section thereofshould be so configured that the ridge will be formed when the slipperseal is positioned around the appropriate member. One form of suitableslipper seal cross section has frustoconical surfaces for surroundingand sealingly engaging one of the members with such surfacessubstantially intersecting centrally of the slipper seal.

This aspect of the invention may also utilize the concept of reducingthe contact between the slipper seal and the member which it sealinglyengages. However, this concept of the invention is not necessarily solimited. The slipper seal may be provided with one or more annulargrooves on the surface thereof which engages one of the members toprovide wiping action.

The invention, both as to its organization and method of operationtogether with further features and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of asealing assembly constructed in accordance with the teachings of thisinvention.

FIG. 2 is an enlarged, fragmentary, axial sectional view through thesealing assembly of this invention with the sealing assembly forming aseal between two members. The sealing assembly is shown with no fluidunder pressure being supplied.thereto. I

FIG. 3 is a fragmentary, sectional view similar to FIG. 2 with fluidunder pressure being supplied to the sealing assembly from the left sideof the sealing assembly.

FIG. 4 is a fragmentary, axial, sectional view of a second form of asealing assembly constructed in accordance with the teachings oftheinvention.

FIG. 5 is a fragmentary, axial, sectional view ofa third form of sealingassembly constructed in accordance with the teaching of this invention.

FIG. 6 is a fragmentary, axial, sectional view of a fourth form ofsealing assembly constructed in accordance with the teachings of thisinvention with the sealing assembly being installed in a groove.

FIG. 7 is a fragmentary, axial, sectional view similar to FIG. 6 withthe sealing assembly being radially compressed between inner and outermembers.

FIG. 8 is a fragmentary, axial, sectional view of a fifth form ofsealing assembly constructed in accordance with the teachings of thisinvention.

FIG. 9 is a fragmentary, axial, sectional view of a sixth form ofsealing assembly constructed in accordance with the teachings of thisinvention with the sealing assembly being installed in a groove.

FIG. 10 is a fragmentary, axial, sectional view of the sealing assemblyof FIG. 9 being radially compressed between inner and outer members.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings andin particular to FIGS. 1 and 2, reference numeral 11 designates asealing assembly constructed in accordance with the teachings of thisinvention. As shown in FIG. 1, the sealing assembly 11 is generallyannular.

As shown in FIG. 2, the sealing assembly 11 provides a seal.

' between an outer member 13 and an inner member or rod 15.

The members 13 and 15 are movable relative to each other and either orboth of the members may reciprocate and/or rotate. The outer member 13circumscribes the inner member 15 and has an annular groove forreceiving the sealing assembly 11, with the groove being defined byaxially spaced end walls 17 and 19 and a circumferential wall 21. Therod 15 has a peripheral surface 23 which is cylindrical in theembodiment illustrated.

The sealing assembly 11 includes an annular slipper seal 25 and anannular elastomeric seal 27 in the form of an O-ring. The slipper seal25 may be constructed of any suitable wear resistant material withplastic material such as polytetrafluoroethylene being one preferredmaterial. The elastomeric seal 27 may be constructed of any suitableresilient, deformable material such as rubber.

As view in axial cross section (FIG. 2) the slipper seal 25 includes acentral portion 29 and end portions 31 and 33 with each of theseportions circumscribing the rod 15. The central portion 29 has acylindrical inner circumferential surface 35 and a coaxial, cylindrical,outer circumferential surface 37 with both of such surfaces beingsubstantially coextensive axially. Accordingly, the central portion 29is of constant radial thickness.

The end portions 31 and 33 are identical and project in opposite axialdirections from the central portion 29. Each of the end portions 31 and33 projects radially outwardly of the peripheral surface-23 as itextends axially outwardly of the central portion 29. Each of the endportions 31 and 33 progressively thicken radially as they extend axiallyoutwardly of the central portion 29.

Specifically, the end portions 31 and 33 have inner circumferentialsurfaces 39 and 41, respectively, which are generally frustoconical andwhich extend radially outwardly of the peripheral surface 23 as theyproject axially away from the circumferential surface 35. Each of theend portions 31 and 33 also have outer circumferential surfaces 43 and45, respectively. The circumferential surfaces 43 and 45 are concave inaxial cross section to thereby tend to center the elastomeric seal 27over the central portion 29.

In an uncompressed condition, the elastomeric seal 27 is generallycircular in radial cross section. When installed as shown in FIG. 2, theelastomeric seal 27 is radially compressed between the central portion29 and the circumferential wall 21 of the groove. Elastomeric seal 27 iscentered axially relative to the slipper seal 25 with such centralorientation tending to be maintained by the slope of the surfaces 43 and45. In this compressed condition, the elastomeric seal 27 engages thefull axial length of the circumferential surface 37 of the centralportion 29 and also engages the axial inner regions of the surfaces 43and 45. With this arrangement, a substantial portion of the forcegenerated through the radial compression of the elastomeric seal 27 actsradially inwardly through the central portion 29 to thereby force thecircumferential surface 35 tightly against the peripheral surface 23.

It will be appreciated from FIG. 2 that the axial dimension of thecircumferential surface 35 is more than nominal, but substantially lessthan the full axial dimension of the slipper seal 25. By way of examplein the embodiment illustrated, the axial dimension of thecircumferential surface 35 is approximately equal to the radius of theelastomeric seal 27 in the unstressed condition.

When little or no fluid under pressure is supplied to the sealingassembly 11, the elastomeric seal 27 forces the circumferential surface35 into sealing contact with the peripheral surface 23. Because of thereduced area of contact between the slipper seal 25 and the peripheralsurface 23 and because the force generated by compression of theelastomeric seal 27 acts radially through the central portion 29, theforce generated by the seal 25 is sufficient to cause formation of agood low pressure seal between the surfaces 23 and 35.

The fluid under pressure passes between the wall 17 and the slipper seal25 to act on the elastomeric seal 27. As the pressure of the fluidsupplied to the sealing assembly 11 increases, the elastomeric seal 27is deformed to the right as shown in FIG. 3 into contact with the endwall 19. Because the elastomeric material of the seal 27 actssubstantially as a liquid when subjected to fluid pressure, it exerts aradial inward force on the slipper seal 25. This has two effects. First,the central portion 29 is urged more tightly into sealing engagementwith the peripheral surface 23 of the rod 15. Secondly, the elastomericseal 27 is urged over the full axial length of the surface 45.Accordingly, the elastomeric seal 27 and the force of the fluid underpressure acting thereagainst tend to urge the end portion 33 radiallyinwardly. As the pressure of the fluid becomes sufficiently high, theend portion 33 is urged radially inwardly as shown in FIG. 3 so that theinner circumferential surface 41 thereof sealingly engages theperipheral surface 23. The circumferential surface 35 of the centralportion 29 remains in fluid tight sealing engagement with the peripheralsurface 23. Accordingly, the area of contact between the slipper seal 25and the peripheral surface 23 increases when fluid under sufficientpressure is supplied to the sealing assembly l1.

If fluid under pressure were supplied to the right end of the sealingassembly 11 as viewed in FIGS. 2 and 3, the elastomeric seal 27 would beurged to the left to ultimately force the end portion 31 into sealingengagement with the peripheral surface 23. Similarly, the groove for thesealing assembly 11 may be located in the rod 15, if desired, in whichevent the elastomeric seal 27 would be located radially inwardly of theslipper seal 25. In either event, the slipper seal 25 would isolate theelastomeric seal from rubbing contact with the members which does notcontain the groove for the sealing assembly.

FIG. 4 illustrates a second embodiment of the invention wherecorresponding parts are designated by corresponding reference charactersfollowed by the letter a. In FIG. 4, a sealing assembly 11a ispositioned in a sealing groove in a member 13a substantially asdescribed hereinabove with reference to FIG. 2. The sealing assembly 11aincludes a slipper seal 25a and an elastomeric seal 27a, both of whichmay be on annular construction and constructed of the same materials asthe corresponding elements shown in FIG. 2. The members 13a and a may beidentical to the corresponding members of FIG. 2 and capable ofcorresponding relative movement. 7

The slipper seal 25a has a central portion 29a and end portions 31a and33a. The central portion 29a has an inner circumferential surface 350which is flat in axial cross section and which is cylindrical to conformto the configuration of the surface 23a. The end portions 31a and 33ahave inner circumferential surfaces 390 and 41a, respectively, which aregenerally frustoconical. It is apparent that the axial length of thesurface 35a is substantially greater than nominal and that the surface35a extends axially for substantially less then the full axial length ofthe slipper seal 25a. Similarly, it is apparent that the surfaces 39aand 41a are substantially more than mere chamfers.

Elastomeric seal 27a differs from the elastomeric seal 27 in that it isof generally rectangular axial cross section in the unstressed. Inaddition, the elastomeric seal 27a extends for substantially the fullaxial length of the slipper seal 25a. Thus, the elastomeric seal 27alies relatively closely adjacent the circumferential walls 170 and 19aof the seal groove which serve to center the elastomeric seal.

With the construction shown in FIG. 4, the'seal 27a is radiallycompressed between the circumferential wall 21a and the surface 47 tothereby urge the surface 35a into tight sealing engagement with thesurface 23a even when no fluid under pressure is supplied to the sealingassembly 11a. Because the elastomeric seal 27a is located centrally inan axial direction relative to the footprint" of the slipper seal 25, asubstantial portion of the force of radial compression is directedradially inwardly through the central portion 29a so that it iseffective in urging the surface 35a against the surface 23a.

The sealing assembly 11a can be dynamically loaded from either endsubstantially as described hereinabove with reference to FIG. 3 tothereby increase the force for maintaining the surfaces 35a and 23a inengagement. Depending upon the strength of the slipper seal 25a and themagnitude of the pressure of the fluid supplied to the sealing assembly11a, the end portions 31a and 33a may or may not flex radially inwardlyrelative to the central portion 29a in response to the application offluid under pressure as shown in FIG. 3.

FIG. 5 illustrates a third embodiment of the present invention in whichparts corresponding to parts shown in FIG. 2 are designated bycorresponding reference characters followed by the letter b. In FIG. 5,the members 13b and 15b may be identical to the members 13 and 15,respectively. The sealing assembly 11b includes a slipper seal 25b andan elastomeric seal 27b.

The slipper seal 25b is substantially identical to the slipper seal 25except that the central portion 29b is elongated axially and the axialdimensions of the end portions 31b and 3312 are reduced. Thus, thesurfaces 35b and 37b are coaxial and cylindrical. The end portions 31b,and 3312 have inner circumferential surfaces 43b and 45b, respectively;however, these surfaces are flat rather than concave in axial crosssection.

The seal 27b is identical to the seal 27 except that the former is ofplus shape in axial cross section. Thus, the seal 27b includes annularaxial projections 49 and 51 extending toward the walls 17b and 19b ofthe seal groove and terminating in close proximity therewith.

The elastomeric seal 27b is radially compressed between thecircumferential wall 21b and the outer circumferential surface 37b ofthe central region 29b. The elastomeric seal 27b does not normallycontact the surfaces 43b and 45 b and accordingly, the full force ofradial compression of the elastomeric seal 27b is directed radiallyagainst the central portion 29b to thereby urge the circumferentialsurface 35b into sealing engagement with the peripheral surface 23b. Theprojections 49 and 51 and the surfaces 43b and 45b tend to maintain theelastomeric seal 11b centered axially relative to the slipper seal 25b.As shown in FIG. 5, the circumferential surface 35b has an axialdimension which is substantially greater than nominal and whichissubstantially less than the full axial dimension of the slipper seal25b. Similarly, the frustoconical surfaces 39b and 41b are substantiallymore than mere chamfers.

At low pressures, the force of radial compression of the elastomericseal 27b represents a substantial portion of the sealing force exertedagainst slipper seal 25b. However, the sealing assembly 11b can beloaded dynamically sustantially as described herein above with referenceto FIG. 3.

FIG. 6 shows an OD. sealing assembly 101 installed in a groove 103 of arod 105. The groove 103 is defined by radial walls 107 and 109 and by acircumferential wall 1 l 1. The sealing assembly 101 includes a slipperseal 113 and a resilient deformable seal 115 which, in the embodimentillustrated is an O-ring of elastomeric material.

The slipper seal 113 has peripheral frustoconical furfaces 1 17 and 119which intersect along a circular line 121 centrally of the slipper seal113. The slipper seal has a central portion 123 and radially thickenedend portions 125 and 127. The slipper seal 113 has a peripheral surface129, the outer ends of which curve to laterally confine the deformableseal 115 and the central region of which is relatively flat in theposition shown in FIG. 6. The slipper seal 113 is resiliently deformableabout a central circumferentially extending axis.

When an outer member or cylinder 131 is installed over the sealingassembly 101, the sealing assembly assumes the configuration shown inFIG. 7. The cylinder 131 has a cylindrical surface 133 which engagesportions of the frustoconical surfaces 117 and 119 and converts theminto a cylindrical sealing surface 135 thereby axially shortening thefrustconical sur faces 117 and 119. The cylindrical sealing surface 135is formed because the diameter of the slipper seal 113 at the circularline 121 forms a medium interference fit with the surface 133 of thecylinder 131. The installation of the cylinder 131 also causes theformation of an annular ridge 137 in the central portion 123. The ridge137 is formed by resilient displacement of the plastic material of theslipper seal 113 which results due to the medium interference fitbetween the slipper seal and the cylinder 131.

The change in cross section between FIGS. 6 and 7 resulting frominstallation of the cylinder 131 has several important effects. First,the interference fit between the cylindrical sealing surface 135 and thesurface 133 assists in providing good low pressure characteristics.Second, the cylinder 131 applies a radial inward force on the seal 115therby radially squeezing the seal. Third, the deformable seal 115 iscompressed radially an additional amount due to the presence of theannular ridge 137. The radial squeeze on the deformable ring 1 15 causesthe latter to urge the slipper seal 113.into even tighter sealingengagement with the surface 133.

The interference fit and the formation of the ridge 137 cooperate toproduce very good low pressure sealing characteristics. In addition, theelimination of the line 121, and the formation of the cylindricalsurface 135 eliminates the rapid wear which would accompany line Contactof the slipper seal 113 against the cylindrical surface 133. Unitloading of the slipper seal 113 remains relatively high in that the endportions of the surfaces 117 and 119 are not in contact with thesurfacel33.

FIG. 8 shows an emodiment of the invention which is quite similar to theembodiment of FIGS. 6 and7. Parts of the embodiment of FIG. 8corresponding to parts of the embodiment of FIGS. 6 and 7 are designatedby corresponding reference numerals followed by the letter a.

The sealing assembly 101a differs from the sealing assembly 101 in threerespects. First, the sealing assembly 101a is an ID. seal whereas thesealing assembly 101 is an OD. seal. Thus the groove 103a is formed inthe cylinder 131a, and the slipper s'eal 113a sealingly engages acylindrical surface 139 of the rod 105a. Second, the ridge 137a ispermanently formed as part of the slipper seal 113a and is not formed asa result of installation of the slipper seal 113a in the groove 103abetween the outer member 131a and the rod 105a.

Third, the slipper seal 113 has an inner peripheral surface 141 which ispermanently cylindrical and does not assume the cylindricalconfiguration merely because the rod 105a is inserted therein. Moreover,every point along the peripheral surface 141 including the end portionsthereof engages the surface 139 and the rod 105a. With thisconstruction, it is preferred to have a heavy diametral interferencebetween the peripheral surface 141 and the surface 139. The sealingassembly 101a functions in substantially the same manner as the sealingassembly 101 in providing good low pressure sealing characteristics.

F IGS. 9 and 10 show another embodiment of the invention which issimilar to the embodiment shown in FIGS. 6 and 7. Parts of theembodiment of FIGS. 9 and 10 corresponding to parts of the embodimentshown in FIGS. 6 and 7 are shown by corresponding reference numeralsfollowed by the leter b. The embodiment of FIGS. 9 and 10 is identicalto the embodiment of FIGS. 6 and 7 except for the presence of twoannular grooves 143 and 145 formed in axially spaced relationship on thefrustconical surfaces 1 17b and 11%. The annular groo ves 143 and 145form the central portion 123b into a crown for the slipper seal 113b.

When the sealing assembly 113b is installed in the groove 103b betweenthe rod 10512 and the cylinder 131b, the slipper seal 113b and thedeformable seal 115b assume the configuration shown in FIG. 10. Theslipper seal 1 13b forms a medium diametral interference with thecylindrical surface 133b and except for the presence of the grooves 143and 145, the configuration of the slipper seals 113b and 113 in theinstalled condition is identical. Thus, the slipper seal 113b has aridge 137b and -a cylindrical sealing surface b formed in the mannerdescribed above in connection with FIGS. 6 and 7. Moreover, the grooves143 and 145 define a sharp boundary for the central portion or crown1231) and this acts to break the oil film on the surface 133b. Thisinsures better wiping action than if such sharp edge were not provided.

The slipper seals and the deformable seals of FIGS. 6 10 may beconstructed of material as described above in connection with FIGS. 1 5.

Although exemplary-embodiments of the invention have been shown anddescribed, many changes, modifications and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

lclaim:

l. A sealing assembly comprising:

a slipper seal of generally ring-like configuration, said slipper sealbeing constructed of a plastic material and said slipper seal includingfirst and second end portions and a central portion axially separatingsaid end portions;

said slipper seal having first and second peripheral surfaces, saidfirst peripheral surface having a low coefficient of friction, saidsecond peripheral surface defining a ridge extending circumferentiallyalong and circumscribing said central portion; and 1 an elastomeric sealhaving a ring-like configuration engaging said second peripheral surfaceand said ridge, one of said seals circumscribing the other of saidseals, said elastomeric seal being devoid of a mating groove to receivesaid ridge when said elastomeric seal is unstressed whereby said ridgeresiliently deforms said elastomeric seal. 1

2. A sealing assembly for use between first and second relativelymovable members wherein at least one of said member has acircumferentially extending wall partially defining a groove, saidsealing assembly comprising:

a slipper seal of ring-like configuration positionable at leastpartially in said groove, said slipper seal including first and secondend portions axially separated by a central portion with each of saidportions being of ring-like configuration;

said central portion having a circumferential surface which is slidablyengageable with said other member, said circumferential surface having arelatively low coefficient of friction;

a resiliently deformable seal positionable in said groove and radiallycompressible between the circumferential wall of said groove and thecentral portion of said slipper seal whereby the slipper sealsubstantially isolates the elastomeric sea] from simultaneous slidingcontact with both of said members; and

means for defining a circumferentially extending annular ridge on saidcentral portion on the side thereof confronting said deformable seal atleast when said seals are in said groove between said members to furtherradially compress said deformable seal radially of said central portionof said slipper seal whereby said deformable seal urges said centralportion tightly against said other member.

3. A sealing assembly as defined in claim 2 wherein said last mentionedmeans includes means responsive to the positioning of said seals in saidgroove between said members for forming said ridge.

4. A sealing assembly as defined in claim 2 wherein said slipper sealhas a circumferential surface for confronting said other member, saidlast mentioned circumferential surface having at least onecircumferentially extending groove therein at least when said seal isinstalled in said groove between said members.

5. A sealing assembly as defined in claim 2 wherein said last mentionedmeans defines said ridge even when the seals are not positioned in saidgroove and between said members.

6. A sealing assembly as defined in claim 2 wherein said central regionis of maximum radial thickness at the center thereof and is of reducedthickness axially outwardly of said center.

7. A sealing assembly as defined in claim 2 wherein said circumferentialsurface extends axially for substantially less than the full axiallength of said slipper seal, said end portions being out of engagementwith said other member at least when the sealing assembly is installedbetween said members and no fluid pressure is supplied thereto.

8. A sealing assembly as defined in claim 7 wherein said central portionhas a second circumferential surface engageable with the deformableseal, said second circumferential surface being substantially flat inaxial cross section when the slipper seal is unstressed.

9. A sealing assembly comprising:

an inner member;

an outer member substantially circumscribing the inner r a slipper sealof ring-like configuration positionable at least partially in saidgroove, said slipper seal including first and second end portionsaxially separated by a central portion with each of said portions beingof ring-like configuration;

said central portion having a circumferential surface which is slidablyengageable with the other of said members, said circumferential surfacehaving a relatively low coefficient of friction and forming aninterference fit with said other member;

a resiliently deformable seal positionable in said groove and radiallycompressible between the circumferential wall of said groove and thecentral portion of said slipper seal whereby the slipper sealsubstantially isolates the elastomeric seal from simultaneous slidingcontact with both of said members; and

means for defining an annular ridge on said central portion on the sidethereof confronting said deformable seal when said seals are in saidgroove between said members to further radially compress said deformableseal radially of said central portion of said slipper seal whereby saiddeformable seal urges said central portion tightly against said othermember.

1. A sealing assembly comprising: a slipper seal of generally ring-likeconfiguration, said slipper seal being constructed of a plastic materialand said slipper seal including first and second end portions and acentral portion axially separating said end portions; said slipper sealhaving first and second peripheral surfaces, said first peripheralsurface having a low coefficient of friction, said second peripheralsurface defining a ridge extending circumferentially along andcircumscribing said central portion; and an elastomeric seal having aring-like configuration engaging said second peripheral surface and saidridge, one of said seals circumscribing the other of said seals, saidelastomeric seal being devoid of a mating groove to receive said ridgewhen said elastomeric seal is unstressed whereby said ridge resilientlydeforms said elastomeric seal.
 2. A sealing assembly for use betweenfirst and second relatively movable members wherein at least one of saidmember has a circumferentially extending wall partially defining agroove, said sealing assembly comprising: a slipper seal of ring-likeconfiguration positionable at least partially in said groove, saidslipper seal including first and second end portions axially separatedby a central portion with each of said portions being of ring-likeconfiguration; said central portion having a circumferential surfacewhich is slidably engageable with said other member, saidcircumferential surface having a relatively low coefficient of friction;a resiliently deformable seal positionable in said groove and radiallycompressible between the circumferential wall of said groove and thecentral portion of said slipper seal whereby the slipper sealsubstantially isolates the elastomeric seal from simultaneous slidingcontact with both of said members; and means for defining acircumferentially extending annular ridge on said central portion on theside thereof confronting said deformable seal at least when said sealsare in said groove between said members to further radially compresssaid deformable seal radially of said central portion of said slipperseal whereby said deformable seal urges said central portion tightlyagainst said other member.
 3. A sealing assembly as defined in claim 2wherein said last mentioned means includes means responsive to thepositioning of said seals in said groove between said members forforming said ridge.
 4. A sealing assembly as defined in claim 2 whereinsaid slipper seal has a circumferential surface for confronting saidother member, said last mentioned circumferential surface having atleast one circumferentially extending groove therein at least when saidseal is installed in said groove between said members.
 5. A sealingassembly as defined in claim 2 wherein said last mentioned means definessaid ridge even when the seals are not positioned in said groove andbetween said members.
 6. A sealing assembly as defined in claim 2wherein said central region is of maximum radial thickness at the centerthereof and is of reduced thickness axially outwardly of said center. 7.A sealing assembly as defined in claim 2 wherein said circumferentialsurface extends axially for substantially less than the full axiallength of said slipper seal, said end portions being out of engagementwith said other member at least when the sealing assembly is installedbetween said members and no fluid pressure is supplied thereto.
 8. AseaLing assembly as defined in claim 7 wherein said central portion hasa second circumferential surface engageable with the deformable seal,said second circumferential surface being substantially flat in axialcross section when the slipper seal is unstressed.
 9. A sealing assemblycomprising: an inner member; an outer member substantiallycircumscribing the inner member, one of said members at least partiallydefining a circumferentially extending groove; a slipper seal ofring-like configuration positionable at least partially in said groove,said slipper seal including first and second end portions axiallyseparated by a central portion with each of said portions being ofring-like configuration; said central portion having a circumferentialsurface which is slidably engageable with the other of said members,said circumferential surface having a relatively low coefficient offriction and forming an interference fit with said other member; aresiliently deformable seal positionable in said groove and radiallycompressible between the circumferential wall of said groove and thecentral portion of said slipper seal whereby the slipper sealsubstantially isolates the elastomeric seal from simultaneous slidingcontact with both of said members; and means for defining an annularridge on said central portion on the side thereof confronting saiddeformable seal when said seals are in said groove between said membersto further radially compress said deformable seal radially of saidcentral portion of said slipper seal whereby said deformable seal urgessaid central portion tightly against said other member.